Equalizing connection for refrigeration systems



R. L. SPARKS Nov. 30, 1937.

EQUALIZING CONNECTION FOR REFRIGERATION SYSTEMS Filed Dec. 3, 1935 Patented Nov. 30, 193? TATES ,EAM

rA'rENr OFFICE EQUALIZING CONNECTION FOR REFRIG'. ERATION SYSTEMS Robert L. Sparks, Clayton, Mo., assignor to Alco Valve Company, Inc, St. Louis, Mo., a cor- Duration of Missouri Application December 3, 1935, Serial No. 52,729

Claims.-

This invention relates to refrigeration systems of that type employing an expansion valve controlling the admission of refrigerant to the evaporator.

5 It is customary in the art to operate the ex- I This arrangement isunscientific and results in ineflicient operation of the system inasmuch as i there is always a pressure drop between the ends of the evaporator, the pressure at the anterior end being relatively high, so that the valve opening pressure of the thermostatic bulb is resisted by the relatively high pressure, retarding the opening of, the valve, and the valve closing movement being accelerated by said relatively high pressure so that-the expansion valve remains in I such a position to restrict the flow to a greater 80 coil attempts to regulate the supply of refrigerant according to refrigerating demands, a spurious control is imposed by the high counter pressure at the anterior end of the coil, in consequence of which the point of thermal satura- 35 tion, which for highest efliciency should be at the extreme posterior end of the evaporator, is

moved progressively forward to an intermediate part of the coil as the load increases, the effect,

of course, being to reduce the capacity of the 40 coil to that part which is anterior to the point of saturation,-

The principal object of the present invention is to make the expansion valve responsive to the true pressure of the suction gas at the evaporator outlet, by the provision of an external equalizer, establishing communication between the diaphragm chamber on' the side opposite the thermostatic pressure, and the outlet end of the evaporator adjacent thepoint of application of the thermostat. With the system so arranged,

the pressure difierence across the diaphragm is' the difference between the saturation pressure in the thermostatic conduit and thepressure below the saturation point in the suction line of the system caused by the superheated condition of the suction gas. Obviously, the valve can only respond to the superheat of the refrigerant when the pressure under the diaphragm is the actual suction gas pressure.

Other objects of the invention will appear as the following description of a preferred and practical embodiment thereof proceeds.

In the drawing throughout the several figures of which the Same characters of reference have been employed to designate identical parts:

Figure 1 is a diagrammatic view of a refrigeration system; I

Figure 2 is a diametricalsection taken through the expansion valve; and

Figure 3 is a'fragmentary view similar to Figure 2, but showing the conventional by-pass from the anterior end of the evaporator in the underside of the diaphragm.

Referring now in detail to the several figures, the system shown diagrammatically. in Figure 1, comprises an evaporator l communicating on the one hand with an expansion valve 2 and on the other with the suction side of the compressor 3, the latter discharging sequentially into the condenser 4 and a receiver 5' which communicates with the expansion valve by way of the liquid refrigerant column 6.

The details of the expansion valve are illu s-,

trated in Figure 2, the same consisting of a body I to which 'is bolted the spring housing 8. The body is bored to form a passage for liquid refrigerant extending in a tortuous, although generally transverse manner from the end of the liquid refrigerant column 6 to the anterior end 9 of the evaporator l. The intermediate part of' this passage is a vertical bore Ill forminga guide for the feathered stem ll having the valve l2 at its lower end which cooperates with a suitable valve seat l3. The valve stem H is connected to a button l4 reciprocable axially of the valve stem in the diaphragm chamber I5 and being secured to the diaphragm I6 which divides said chamber. The part of the valve stem l1 adjacent the button It passes through a packing gland which prevents liquid refrigerant entering the diaphragm chamber. The valve is normally biased into closed position by a spring l8 occupying a bore in the spring housing 8. The tension'of said spring can be adjusted by means of a threaded stem Ill. The diaphragm l6 controls the opening and closing movements of the valve l2. The upper part of the diaphragm chamber is in communication by way of the tube 20 with a thermostatic bulb 2| shown in Figure l and which is secured in heat-exchanging relaend thereof.

tion tothe evaporator I equalizing tube 22 is connected to the suction end of the refrigerant conduit adjacent the outlet end of the evaporator and communicates at its opposite end with the opposite -side of the diaphragm chamberopposing a resistance to the valve opening bias imparted by the thermostatic bulb. Thus, since the actuating pressure within the bulb and the pressure transmitted by the equalizer 22 upon opposite sides of the valve-actuating diaphragm are derived from closely adjacent positions at the posterior or outlet end of the evaporator, it is obvious that the actuation of the expansion valve will respond to the true suction pressure of the evaporator and not to the spurious or artificial pressure at the anterior end of the evaporator,

This means of imposing the true pressureof the suction gas at the evaporator outlet, on the underside of 'thevalve operating diaphragm avoids excessive change of the controlled superheat of the suction gas at the point of application of the bulb. Changes in superheat are caused by the inherent characteristics of all tube or tank type evaporators which show an appreciable pressure drop from inlet to outlet, the same being a function of the load on the evaporator. As the load increases, the flow increases and consequently, the pressure drop becomes greater. In the older type of construction illustrated in Figure 3, in which the relatively high pressure at the anterior end of the evaporator is transmitted to the underside of the diaphragm by'means such as the passage 23, the pressure compensation on the underside of the diaphragm is such that its relation to the thermostatic pressure above the diaphragm causes the expansion valve to be maintained in a relatively restricted position by the excessive pressure tending to close it with an increased flow of refrigerant through the evaporator. Thus, it will be apparent that progressive increase in controlled superheat will result at the point of remote bulb application, and as the pressure drop increases, less percentage of the'total surface area of the evaporator will be rendered effective for the absorption of the latent heat evaporation of the refrigerant, because of the progressive movement of the point of saturationtoward the evaporator inlet. This makes'it obvious that the efficiency of the evaporator is reduced as the refrigerating demand grows greater.

Under the present invention, by imposing the true pressure at or nearthe point of remotebulb application to the diaphragm on the side opposite to that afiected by the thermostatic pressure, the pressure differential across the diaphragm is the difference between the saturated pressure in the thermostatic bulb conduit and the pressure below the saturation point in the suction line caused,

at, the outlet or suction the thermostatically operated expansion valve is to control the refrigerant flow in such manner as to permit the maximum evaporator surface effective for the transfer of latent heat to the vaporizing refrigerant, it is essential that a true pressure of the gas at the evaporator outlet be used as a compensating force. This insures a maximum efiiciency consistent with rapid response and freedom from cycling or hunting caused by the momentary imposition of false pres- I sures due to the spasmodic slugging or feeding of the valve and consequent irregular pressure drops across the evaporator tube or tank. The present invention reduces the amplitude of these waves of pressure bythe restriction in flow through the tube and by the conversion of the liquid into a gaseous state.

While I have in the above description disclosed what I believe to bea preferred and practical embodiment of the invention, it is to be understood by those skilled in the art that the principle of the invention is broad and that the specific details of construction are merely by way of example and may be modified both in structure and arrangement to suit the exigencies of use without transcending the scope of the appended claims.

I What I claim is:

1. In a refrigeration system, an evaporator intercalated between the usual high and low sides of said system, a valve controlling the admission of liquid refrigerant to said evaporator, pressureresponsive means for operating said valve, said operating means being actuated proportionately to th variable resultant pressure of opposed pressuresyone varying directly with the temperature of the evaporator adjacent the outlet and the other being the pressure of the refrigerant at a point in the system adjacent the outlet of the evaporatonand varying directly with the load on the evaporator.

2. In a refrigeration system, an evaporator in-.

,tercalated between the usual high and low sides of said system, a valve controlling the admission of liquid refrigerant to said evaporator, a diaphragm for operating said valve, said diaphragm being actuatedproportionately to the variable resultant pressure of pressures imposed upon opposite sides of said diaphragmmne varying directly with the temperature of the evaporator adjacent the outlet and the other being the pressure of the refrigerantat a point in the system adjacent the outlet of the evaporator, and varying directly with the load on the evaporator.

- 3. In a refrigeration system, an evaporator intercalated between the usual high and low sides of said system, an expansion valve controlling the admission of liquid refrigerant to said evaporator, a diaphragm for operating said valve, a thermostatic bulb positioned' adjacent the outlet end of said evaporator for imposing pressure upon said diaphragm in a valve-opening I direction, and means communicating with the evaporator adjacent its outlet end, and with the opposite side of said diaphragm for imposing the true suction pressure of said evaporator upon saiddiaphragm in a valve-closing direction.

4. In a refrigeration system, an evaporator intercalated between the usual high and low sides I of said system, an expansion valve controlling the admission of.liquid refrigerant to said evaporator, a diaphragm for operating said valve, a thermo-- a valve-opening direction, and means for imposing a counter-pressure upon the opposite side of said diaphragm derived from a point in said system adjacent the outlet end of said evaporator, whereby to decrease the fluctuating of superheat arising during the cycling periods of said system.

5. In a refrigeration system, an evaporator intercalated between the usual high and low sides of said system, a valve controlling the admission of liquidrefrigerant to said evaporator, pressure responsive means for operating said val-ve said operating means being actuated proportion- I ately to the variable resultant pressure of opposed pressures, one varying directly with the temperature .of the evaporator adjacent the outlet, and the other being the pressure of the refrigerant at Ya point in.the system remote from the point at which liquid refrigerant is admitted to the sys-- tem and varying directly with the load on the evaporator.

ROBERT L. SPARKS. 10

DISCLAIMER 2,100,494.Robert L. Sparks, Clayton, M0. EQUALIZING CONNECTION FOR RE- FRIGERATION SYSTEMS. Patent dafoed November 30, 1937. Disclaimer filed September 15, 1938, by the assignee, Also Valve Company. Hereby enters this disclaimer to claims 3 and 4.

[Ofiicial Gazette October 11, 1938.] 

